Pyrgocythara turrispiralata, Scarponi & Bella & Dell’Angelo & Huntley & Sosso, 2016
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publication ID |
https://doi.org/ 10.4202/app.00158.2015 |
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persistent identifier |
https://treatment.plazi.org/id/A8608798-FF8F-FFB8-1F63-7081FDA54544 |
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treatment provided by |
Felipe |
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scientific name |
Pyrgocythara turrispiralata |
| status |
sp. nov. |
Pyrgocythara turrispiralata View in CoL sp. nov.
Figs. 6C View Fig , 7B View Fig , 8A, B View Fig ; SOM 1: fig. 3G, SOM 2.
Etymology. From Latin turris, tower, and Greek speira, spire; named after the characteristic turreted spire.
Type material: Holotype, MGGC-24514 , adult, well-preserved shell . Paratypes, MGGC-24515 /1–14 from the type locality (SOM 2) .
Type locality: Horodok , Ukraine .
Type horizon: Weakly-cemented sandstone, attributed to the Pidhirtsi Beds, early Serravallian (~14.0−12.7 Ma).
Material. — Twenty-two topotype specimens from Horodok: IGS-NANU-B-I-33-35/2015 (3 shs), MNHN.F.A53763 (3 shs); MSNG-58191 (3 shs), MGPT-PU135048 (3 shs), MZB-32058 (4 shs), NHMW-2015 /0404/0005 (3 shs), ZISP-62078 (3 shs) and one (not well preserved) from Varovtsi: IGS-NANU-B-I-33/2015 .
Diagnosis. — A medium-sized Pyrgocythara (shell lengthm 6.3 mm, sd 0.6 mm; shell widthm 2.9 mm, sd 0.3 mm), with a multispiral, conical-shaped protoconch (widthm 0.60 mm, sd 0.04 mm) and characterised by a few, strongly curved riblets. The teleoconch shows a turreted spire (0.33 the shell lengthm, sd 0.03) and a noticeable spiral pattern of strong cords on spiral whorls (commonly 3 on the second whorl); the last whorl is elongated and varicose, bearing a sub-rectangular and narrow aperture.
Description. — Shell small-sized, fusiform; spire strongly turreted (0.33 the shell lengthm, sd 0.03); last whorl slightly rounded, elongated (lengthm 4.2 mm, sd 0.4 mm), varicose. Protoconch conical, of 2.5−2.2 whorls, nucleus very small, smooth as the remaining whorls except for few opisthocline, curved axial riblets in the final-quarter; protoconch-teleoconch boundary abrupt, marked by a sinusigera. Teleoconchm of 4.1 whorls (sd 0.3 wh), flattened in profile, with both strong axial and spiral sculpture; suture almost straight. Axial sculpture of prominent, slightly opisthocline, rounded and spaced ribs (usually 9 on second whorl), extending across the sutures on spiral whorls, until the base on last whorl; growth lines occasionally evident. Spiral pattern of relatively thick, widely spaced cords (usually 3 on second whorl) separating small groups of very thin threads indented by growth lines; on sutural ramp threads less homogeneous than below periphery. Aperture elongated (mean 2.9 mm, sd 0.3 mm), narrow, sub-rectangular; outer lip almost straight in profile, internally thickened. Anal sinus relatively wide, C-shaped, bearing (inside the outer lip) a swollen tubercle; siphonal canal very short, clearly distinct; columellar lip almost straight.
Remarks. — Various authors have already documented few species that show morphological similarities to P. turrispiralata sp. nov. for the Central Paratethys and Mediterranean areas. Among others, Friedberg (1951) and Bałuk (2003) report: (i) Clathromangelia clathrata ( Serres, 1829) from the Miocene of Ukraine and Poland; (ii) Mangelia monterosati Bellardi, 1877 from the Ukraine ( Friedberg 1951); (iii) Mangelia contracta Bellardi, 1877 from Poland ( Bałuk 2003). Clathromangelia clathrata shows a somewhat comparable shell outline and teleoconch ornamental pattern; however, it can be easily differentiated from P. turrispiralata by its ( Raphitoma -like) protoconch sculpture and the teleoconch spiral ornamentation, consisting of two prominent cords on spiral whorls (for further details see Glibert 1954; Bałuk 2003).
In reference to Mangelia monterosati , the type material is missing ( Ferrero Mortara et al. 1981). Regrettably, the original description and accompanying iconography do not provide sufficient detail to characterise the species. Consequently, it should be considered a nomen dubium.
The type material of M. contracta is housed at the Museo Regionale di Scienze Naturali in Turin ( Italy). Ferrero Mortara et al. (1981) illustrated the two syntypes; both show more flattened and tall teleoconch whorls, with less numerous ribs (max. 9) and more numerous spiral elements than P. turrispiralata (see also Bellardi 1877). Unfortunately, both specimens are lacking the apex and thus the highly diagnostic protoconch features cannot be evaluated. At the present time M. contracta cannot be precisely characterised until new material from the type locality is found.
Lastly, Pyrgocythara rugosissima ( Seguenza, 1875) , an extinct Mediterranean Pliocene mangeliid ( Tucker 2004; Scarponi and Della Bella 2010; SOM 1: fig. 4I), is morphologically comparable to P. turrispiralata , in particular with regard to the aperture and sinus morphology and the teleoconch sculpture. However, detailed quantitative comparison of shell characters between batches of specimens allowed a clear separation of the two allied species ( Fig. 2 View Fig , SOM 2). P. rugosissima shows a notably larger protoconch (e.g., widthm 0.73 mm, sd 0.03) and the final one and half whorls bear ornamentation, whereas P. turrispiralata is smaller (e.g., widthm 0.60, sd 0.04) bearing ornamentation only on its final quarter for further details see Fig. 2 View Fig , SOM 2). In addition, all the measured teleoconch features (except for spiral sculpture) show reduced or no overlap between the two taxa, with P. rugosissima showing smaller values than those of P. turrispiralata (see Fig. 2 View Fig , SOM 2) and relevant statistical tests allow us to reject the null hypothesis (i.e., no difference between the two samples) for all features ( Table 1) except for the major threads on the second whorl (i.e., 2.7 vs. 2.9, p = 0.42; SOM 3).
Stratigraphic and geographic range.—Pidhirtsi Beds, early Serravallian of the Central Paratethys.
| MNHN |
Museum National d'Histoire Naturelle |
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